Secure Spectral-Energy Efficiency Tradeoff in RandomCognitive Relay Networks

• Published in: 中国通信：英文版 Vol. 14; no. 12; pp. 45 - 58
• Main Author: Bing Wang;Kaizhi Huang;Xiaoming Xu;Yi Wang
• Format: Journal Article
• Language: English
• Published: 2017
• Subjects: physical;layer;security;;cognitiverelay;networks;;secure;spectral;efficiency;secure;energy;efficiency;;spectral-energy;effi-ciency;tradeoff
• ISSN: 1673-5447

Spectral efficiency （SE） and ener-gy efficiency （EE） in secure communicationsis of primary importance due to the fact that5G wireless networks aim to achieve highthroughput, low power consumption and highlevel of security. Nevertheless, maximizingSE and EE are not achievable simultaneously.In this paper, we investigate the SE and EEtradeoff for secure transmission in cognitiverelay networks where all nodes are randomlydistributed. We first introduce the opportunis-tic relay selection policy, where each primarytransmitter communicates with the primaryreceiver with the help of a secondary user as arelay. Then, we evaluate the secure SE and se-cure EE of the primary network based on theoutage probabilities analysis. Thirdly, by ap-plying a unified SE-EE tradeoff metric, the se-cure SE and EE tradeoff problem is formulat-ed as the joint secure SE and EE maximizationproblem. Considering the non-concave featureof the objective function, an iterative algo-rithm is proposed to improve secure SE andEE tradeoff. Numerical results show that theopportunistic relay selection policy is alwayssuperior to random relay selection policy.Furthermore, the opportunistic relay selectionpolicy outperforms conventional direct trans-mission policy when faced with small securitythreat （i.e., for smaller eavesdropper density）.